It comes amid mounting speculation the Scot will make the move south to Westminster before the next General Election.

She said: “The obvious question is: where should this money come from? I have no doubt that this will be the source of major debate within our party and across parliament over the coming months. Indeed, it has already started.

“My view is this: the UK Government has acted to reduce the tax burden on working families. It has honoured its promise to do so. Raising the income tax threshold has reduced taxes for millions of UK workers and has taken thousands out of taxation altogether.

“But the UK Government has a choice to make. And, if that choice is between extra spending on the NHS or introducing further tax breaks beyond those already promised, I choose the NHS.”

Middle earners in England have been given income tax cuts in recent years and are in line for more under Tory manifesto pledges. But the SNP have effectively edged up charges for the same bracket north of the border.

For England, Wales and Northern Ireland, the Tories have pledged to increase the personal allowance to £12,500 by 2020 and the 40p higher rate threshold to £50,000 by 2020. The currently levels are are £11,850 and £46,350.

In Scotland, the higher rate threshold has been kept at £43,430 - the level in the rest of the UK before the devolved income tax system kicked in from April 2017.

In the speech, titled Building a Stronger Britain, Ms Davidson said the NHS had “dealt brilliantly” with growing demand over the last decade, by “finding new ways to deliver and improve the standard of care”.

But pointing to Lord Darzi’s review to mark thus year’s 70th anniversary of the NHS, she said we we are “now reaching a tipping point”.

She said: “The simple choice is this: if we want to continue to adhere to the principles of our NHS – then we need to find extra funding above and beyond the increases of recent years.

“So as we prepare to mark the 70th anniversary of the NHS later this summer, I very much support the proposal for substantial extra funding across the whole of the UK to put the NHS on a firm and solid footing for the long term.”

Elsewhere in her speech, she repeated concerns about the UK Government’s target - unmet since it was introduced in 2010 - of cutting net migration to below 100,000.

Latest stats, for the year ending last September, show 244,000 more people came to the UK than left - a similar level to early 2014.

Ms Davidson called for a “review” of the aim earlier the month and last year she questioned if the target “continues to be the right one”.

And last night/tonight she said: “I have said this before but I will repeat it tonight: I see neither the sense nor the need to stick to an immigration figure devised nearly a decade ago, which has never been met and does not fit the requirements of the country.

“Setting an immigration target reduced to the tens of thousands is one thing when unemployment is running eight per cent.

“Refusing to review it when the country nears full employment and sectors are reporting skills shortages is quite another.”

She also repeated calls for overseas students to be removed from the figures, saying: “Even if that target were to stay, I see no reason why overseas students should be included within the numbers counted.

“And, after leaving university, I would also like to see graduates hailing from other countries, but trained here, given more opportunities to stay in Britain so they can continue to put that UK academic investment to the common good.”

On the climate after the EU referendum, she added: “It’s been notable that, since the Brexit vote, polls have shown that concerns over immigration are actually reducing. It is not a side-effect I had foreseen from the vote, but, if sustained, I believe it is a positive one.

Ruth Davidson tells PM plotters to pipe down and put​ ​country over ambition

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“Brexit requires the country to make decisions at a UK level on aspects of immigration previously held by Brussels. As we have to shape those arrangements, I hope we can create a mature system, which leads to a more settled country.”

In the speech - part of the Policy Scotland series of lectures - she also suggested “rigorous, sustained work experience” for school-age youngsters should “become the norm, not the exception”.

She added: “I think vocational and technical education should become an integral part of the school day, not an unusual add-on.”